Sergeant Thosath was a member of Company I, 3rd Battalion, 7th Marines, 1st Marine Division. He was listed as Missing in Action while fighting the enemy in Korea on 2 December 1950. He was presumed dead on 7 December 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Thosath was awarded the Purple Heart, the Combat Action Ribbon, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.